1.08.2012

CARDIOGENIC SHOCK

Posted on 11:27 PM by know about heart

Shock may be defined as inadequate tissue perfusion due to absolute or relative decrease of blood volume. It is the final pathway for several lethal clinical events, including severe hemorrhages extensive trauma or burns, large myocardial infarction, pulmonary embolism and myocardial sepsis.
Types of shock:
   1. Cardiogenic shock
   2. Hypovolemic shock
   3. Septic shock
Cardiogenic shock:
It results from low cardiac output due to failure of cardiac muscle (myocardium) to pump. It can be due to intrinsic to myocardial damage (infarction), ventricular arrhythmias, extrinsic compression (cardiac temponade) or outflow obstruction. Shock in acute myocardial infarction occurs when the left ventricle fails to perform its pumping function. However it may also occur due to right ventricular failure and variety of complication including temponade, an acquired ventricular septal defects and acute myocardial regurgitation. Severe systolic dysfunction of heart muscle, cause a fall in cardiac output. We know the equation is that:_
          BLOOD PRESSURE=CO (cardiac output) * TPR (total peripheral resistance)
So when cardiac output decrease there is also fall in blood pressure and thereby coronary perfusion pressure. When diastolic dysfunction occur it cause a rise of left ventricular diastolic pressure, pulmonary congestion, edema and hypoxia which in turn worsen myocardial ischaemia. In cardiac temponade there is also decrease cardiac output and shock occurs.

SIGNS AND SYMPTOM:
   1. Hypotension
   2. Tachycardia
   3. Cold, clammy skin
   4. Rapid shallow breathing
   5. Decrease volume of urine and sometimes anurea
   6. Myocardial depression
   7. Confusion
   8. Intracerebral bleeding

TREATMENT OF SHOCK:
Stage 1: General measure:-
   §Analgesia
   §Oxygen via MC mask or ventilation if necessary
   §Insertion of monitoring lines:-Swan-Gang catheter introduced, redial artery canulation
Stage 2:      Correction of filling pressure:-
As soon as Swan-Gang catheter is in situ, attempts are made to get the LVEDP/PAW PRESSURE TO 16 TO 18 mmHg. This is the optimum filling pressure.
a. Filling pressure too high-
  With normotension (aortic pressure >90 mmHg)_ Vasodilators is used to keeping mean aortic pressure>70mmHg.
With hypertension:-Dopamine 5 to 10 microgram/Kg/min
b.Filling pressure too low_
Often caused by combination of right ventricular infarction and hypovolaemia due to a reduced oral intake of fluids, vomiting and inappropriate diuretic therapy. These patients are managed by IV fluid therapy.
Stage 3: Improvement of stroke volume:-
Inotropes are usually required. Dopamine should be initiated promptly to raise mean arterial blood pressure and be maintained at the minimum dose required. Dobutamine may be combined with Dopamine at moderate dose or used alone for a low output state without frank hypertension. Both Dopamine and Dobutamine have their advocate.
Stage 4: Early definition of coronary anatomy:-
   Coronary angiography
Stage 5: Further measures:-
  Support by Intra aortic ballon pumping (IABP) while arrangements are being made for further measures. IABP can now be inserted precutaneously. The R wave of the ECG triggers balloon deflation. The balloon is timed to inflate just after the dicrotic notch of aortic valve closure. Inflation increase coronary cerebral flow. Hilium is used as inflation gas.

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